The Eureka lemon, one of the most common lemon crops in California, is a prolific fruit producer with a long season. The only time it does not produce is autumn. As a standard tree, it can grow 8 feet in height but, if grafted to a different rootstock (usually Flying Dragon) the trees are smaller. Grafted trees grow about 3 feet tall and can be arching or bushy in habit. They are hardy in zones 6 to 11, although as heat lovers, they really need to be sheltered when temperatures dip below 32 degrees F. They are evergreen and have blooms on them almost year round.
The Eureka lemons were first discovered among seedlings in Los Angeles, CA in the 1850s. The seedlings had sprung from Italian citrus seeds. The trees usually won't produce fruit for decades if grown from seed, so grafting is an important way to increase the rooting process and stimulate the tree to produce. Grafting is usually done when the tree is no longer dormant.
Foliage Damage Caused by Insects
Aphids are common on citrus, but are temporary pests, lasting only six weeks. The insects can be controlled with an insecticidal soap. More damaging are leaf miners, which eat the inside of the leaf, leaving a silver sheen and deforming the leaves. Affected leaves should be removed and an organic pesticide with spinosad can be applied. Scab is common, as are mites, with both pests controlled by a 1 percent solution of ultrafine horticultural oil spray.
Foliage Damage Caused by Disease
The citrus plant is plagued by powdery leaf mildew. This leaves a sooty coating on the leaf, but is more cosmetic than damaging. Wipe the leaves clean to keep the stoma open and give the plant oxygen. The mold comes from aphid secretions so the best way to stop it is with an insecticidal soap. Citrus canker causes leaves to get circular scabs and lesions and can be controlled with a copper fungicide. Several other fungi can deform or maim leaves but most are fungus that can be controlled with a copper fungicide spray.
Leaf deformity will not cause a loss of crop; it is just unsightly. As long as the problem is identified and the rest of the tree looks healthy, generally the deformed leaves can be removed and new ones allowed to grow. If the problem persists in spite of the treatment, take a leaf to your local college extension or nursery to get a better diagnosis.
The Eureka lemon is easy to take care of. It is not as tolerant of cold as a Meyer, so should be kept away from drafts and air conditioners if grown indoors. Watering well once a week in a well-drained pot, monthly citrus fertilizer in its growing season and five to six hours of sunlight, will produce a healthy, glossy plant.